Conventional safety helmets comprise an impact resistant, hard external shell and an inner shock-absorbent liner which is contoured to fit and protect the head of the wearer. Usually, the shock-absorbent portion of the helmet is made of a low-density soft material, such as expanded polystyrene foam, which is easily damaged and soiled during handling.
U.S. Pat. No. 4,996,724 dated Mar. 5, 1991 and entitled: PROTECTIVE RIM CONFIGURATION FOR HARD SHELL SAFETY HELMET--inventor: Serge Dextrase, partially overcomes the above-noted disadvantage, by providing a rim configuration made of the same hard material as the external shell and covering the lower periphery of the external shell. However, in such a helmet, the polystyrene foam is still left exposed inside the helmet.
In order to have sufficient impact resistance, the liner of such a helmet must be relatively thick or the foam material of said liner must have a relatively high density, for instance 6 pounds per cubic foot.
Another problem with existing safety helmets is that, once they have sustained a first major blow, they tend to fracture, become fragmented and to fall apart--the fragmented parts thereof release one another. This is to say, the helmet disintegrates. This is unfortunate, since in high-speed cycling accidents, multiple ground impacts of the head are not uncommon. If the helmet has already fragmented and disintegrated after the first ground impact, it becomes useless in preventing head injuries for the following ground impacts of the behelmeted cyclist.